The Barley Heavy Metal Associated Isoprenylated Plant Protein HvFP1 Is Involved in a Crosstalk between the Leaf Development and Abscisic Acid-Related Drought Stress Responses.

The heavy metal associated isoprenylated plant proteins (HIPPs) are characterized by at least one heavy metal associated (HMA) domain and a C-terminal isoprenylation motif. Hordeum vulgare farnesylated protein 1 (HvFP1), a barley HIPP, is upregulated during drought stress, in response to abscisic acid (ABA) and during leaf senescence. To investigate the role of HvFP1, two independent gain-of-function lines were generated. In a physiological level, the overexpression of HvFP1 results in the delay of normal leaf senescence, but not in the delay of rapid, drought-induced leaf senescence. In addition, the overexpression of HvFP1 suppresses the induction of the ABA-related genes during drought and senescence, e.g., HvNCED, HvS40, HvDhn1. Even though HvFP1 is induced during drought, senescence and the ABA treatment, its overexpression suppresses the ABA regulated genes. This indicates that HvFP1 is acting in a negative feedback loop connected to the ABA signaling. The genome-wide transcriptomic analysis via RNA sequencing revealed that the gain-of-function of HvFP1 positively alters the expression of the genes related to leaf development, photomorphogenesis, photosynthesis and chlorophyll biosynthesis. Interestingly, many of those genes encode proteins with zinc binding domains, implying that HvFP1 may act as zinc supplier via its HMA domain. The results show that HvFP1 is involved in a crosstalk between stress responses and growth control pathways.

Lichen as Micro-Ecosystem: Extremophilic Behavior with Astrobiotechnological Applications.

This work demonstrates the tolerance of lichen Pleurosticta acetabulum under extreme conditions similar to those encountered in extraterrestrial environments. Specifically, the impact of three extreme Mars-like conditions-complete dehydration, extremely low temperature (-196°C/77K), and oxygen depletion-on lichens was investigated. The symbiosis of mycobiont and photobiont partners creates a micro-ecosystem that ensures viability of both symbiotic partners under prolonged desiccation and extremely low temperatures without any cultivation care. Changes in the molecular structure and function of the photosynthetic apparatus, in the level of chlorophylls, polyamines, fatty acids, carbohydrates, ergosterol, efflux of K+, and DNA methylation ensure the ecological integrity of the system and offer resistance of lichens to above-mentioned extreme environmental conditions. For the first time, we also demonstrate that the unprecedented polyextremophilic characteristic of lichens could be linked to biotechnological applications, following exposure to these extreme conditions, such that their ability to produce a high yield of hydrogen was unchanged. All these support that lichens are (a) ideal model systems for a space mission to inhabit other planets, supporting also the aspect that the panspermia theory could be extended to incorporate in the traveling entities not only single organisms but micro-ecosystems like lichens, and (b) ideal model systems for astrobiotechnological applications (hydrogen production), such as in the development of bioregeneration systems for extraterrestrial environments.

Bioenergetic reprogramming plasticity under nitrogen depletion by the unicellular green alga Scenedesmus obliquus.

MAIN CONCLUSION: Simultaneous nitrogen depletion and 3,4-dichlorophenol addition induce a bioenergetic microalgal reprogramming, through strong Cyt b 6 f synthesis, that quench excess electrons from dichlorophenol's biodegradation to an overactivated photosynthetic electron flow and H 2 -productivity. Cellular energy management includes "rational" planning and operation of energy production and energy consumption units. Microalgae seem to have the ability to calculate their energy reserves and select the most profitable bioenergetic pathways. Under oxygenic mixotrophic conditions, microalgae invest the exogenously supplied carbon source (glucose) to biomass increase. If 3,4-dichlorophenol is added in the culture medium, then glucose is invested more to biodegradation rather than to growth. The biodegradation yield is enhanced in nitrogen-depleted conditions, because of an increase in the starch accumulation and a delay in the establishment of oxygen-depleted conditions in a closed system. In nitrogen-depleted conditions, starch cannot be invested in PSII-dependent and PSII-independent pathways for H2-production, mainly because of a strong decrease of the cytochrome b 6 f complex of the photosynthetic electron flow. For this reason, it seems more profitable for the microalga under these conditions to direct the metabolism to the synthesis of lipids as cellular energy reserves. Nitrogen-depleted conditions with exogenously supplied 3,4-dichlorophenol induce reprogramming of the microalgal bioenergetic strategy. Cytochrome b 6 f is strongly synthesized (mainly through catabolism of polyamines) to manage the electron bypass from the dichlorophenol biodegradation procedure to the photosynthetic electron flow (at the level of PQ pool) and consequently through cytochrome b 6 f and PSI to hydrogenase and H2-production. All the above showed that the selection of the appropriate cultivation conditions is the key for the manipulation of microalgal bioenergetic strategy that leads to different metabolic products and paves the way for a future microalgal "smart" biotechnology.